1. Field of the Invention
This invention relates generally to heat exchangers and more particularly to contact interfaces between two heat exchangers.
2. Background Art
There is taught a thermal operated circuit controlling device in U.S. Pat. No. 2,109,169. The device provides for adjustment of the time of operation of bi-metallic thermal elements enclosed in an evacuated or gas filled bulb. A diaphragm is provided as a means of varying the pressure within the device for the purpose of adjusting the operating time of a thermally operated circuit controller.
In U.S. Pat. No. 3,225,820 there is taught a device for maintaining the operating temperature of an electronic component by controlling the rate at which the heat generated within the component is allowed to dissipate. A bellows containing an expansive medium expands and contracts to vary an air gap, the bellows itself serving as a heat conductor and the width of the air gap serving to control the resistance to heat dissipation.
A heat valve is taught in U.S. Pat. No. 3,391,728. The heat valve is formed in the gap between the heat source and a heat sink. The gap is capped on one end by a pressurized gas reservoir and on the opposite end by a bellows containing a liquid thermal conductor. By varying the level of the liquid thermal conductor, the conduction of heat across the gap can be controlled.
In U.S. Pat. No. 3,450,196 there is taught an apparatus which uses gas pressure control to vary thermal conductivity. A heat radiating component is surrounded with multiple layers of thermal insulation with the outer layer of the thermal insulation being a pressurizable container. Gas or liquid may be passed between the layers of thermal insulation and by varying the pressure of the gas or liquid, the thermal conductivity of the gas or liquid is varied resulting in a regulation of the heat loss of the component.
In U.S. Pat. No. 3,463,224 there is described a heat transfer switch which utilizes a contained fluid, a bellows and heat conducting plate. As the temperature of the fluid is increased, it expands filling the bellows with the bellows in turn elongating and driving one thermal conducting plate to contact another.
In U.S. Pat. No. 3,478,819 there is taught a variable heat conductor for use in space vehicles. A thermal responsive element is used to drive an actuator causing a piston to contact a heat sink.
A thermal coupling device for use in cryogenic refrigeration is taught in U.S. Pat. No. 3,807,188. The device incorporates a mercury filled bellows. When the mercury freezes the bellows clamps around a thermal transfer neck, thus providing a coupling between a refrigerant source and a device to be refrigerated.
A double tube heat exchanger is taught in U.S. Pat. No. 3,907,026. The heat exchanger is conventional in that heat is transferred from a primary fluid to a secondary fluid. The tubes through which the fluids flow are interdigitated.
Building panels having controllable insulating capabilities are taught in U.S. Pat. No. 3,920,953. The panels comprise a pair of walls which can be moved toward or away from each other to vary the insulating properties of the panels. Air is used to inflate flexible ducts residing between the walls, thus driving the walls further apart to increase the insulating properties of the panel. Deflating the flexible ducts draws the walls together and decreases the insulating properties of the panel.
U.S. Pat. No. 3,957,107 teaches yet another thermal switch connecting a heat sink to a heat source. An expandible bellows encloses a refrigerant. As the bellows assembly is heated, the refrigerant vaporizes expanding the bellows and connection the heat circuit between the heat sink and the heat source.
yet another heat controlling device utilizing a bellows arrangement is taught in U.S. Pat. No. 4,454,910. As with some other patents discussed above, the bellows encloses a working fluid with a relatively high vapor pressure As the working fluid is heated, the resultant vapor pressure causes the bellows to expand thereby driving a contact plate toward a radiating plate. Heat from a heat source is then transmitted through the working fluid and the contact plate to the radiating plate.
Although it can be seen that heat transfer devices have incorporated bellows to drive contacting plates together to complete a heat circuit, the use of a bellows has not been incorporated to drive multiple plate-type heat exchangers into contact with a second plate-type heat exchanger in an interdigitated arrangement. Further, nowhere has there previously been used a thin membrane diaphragm forming an end portion of the bellows to allow the surface of the membrane diaphragm to conform to any contours in the heat exchanger plates thereby applying a uniform contact pressure between the heat exchangers. The result is a dry, efficient heat transfer where the rate of heat transfer can be varied by varying the pressure within the bellows.